This program is concerned with analysis of peptide hormone receptors in testis and ovary, with particular reference to the control of receptor concentration by changes in homologous and heterologous hormones. Desensitization of gonadal adenylate cyclase and steroidogenic responses by gonadotropic hormones is followed by receptor loss and turnover or processing of the hormone-receptor complex. These processes were investigated in Leydig cells and ovarian luteal cells to determine the effects of hormone-induced receptor regulation on gonadal responsiveness, and to analyze the mechanism and consequences of target-cell desensitization. The receptor and direct actions of gonadotropin-releasing hormone (GnRH) in the ovary and testis were also characterized, and analyzed in relation to the recently discovered anti-gonadal effects of GnRH agonists.